MTC brings very different characteristics to the current mobile communications system such as extremely power constrained, mostly very low data-rate, intermittent data, very large number of devices and generally low mobility. The SAE (System Architecture Evolution)/LTE (Long Term Evolution) system can be optimized for these MTC characteristics and thus architecture enhancements may be needed which can 1) cater for the MTC characteristics, while 2) minimizing impact on current network is needed.
Note that the architecture of MTC has been studied in NPLs 1 and 2, for example.